DIPOLE-MOMENTS OF 7 REFRIGERANTS

Dielectric constant measurements have been performed on seven refrigerants in the gaseous state over the range 305-415 K in order to determine their dipole moments. Four of the refrigerants have temperature-independent moments: R123 (1,1-dichloro-2,2,2-trifluoroethane), mu = 1.356 +/- 0.019 D; R141b (1,1-dichloro-1-fluoroethane), mu = 2.014 +/- 0.018 D; R22 (chlorodifluoromethane), mu = 1.458 +/- 0.003 D; and R32 (difluoromethane), mu = 1.978 +/- 0.007 D. Two refrigerants have conformer-dependent moments, making their time-averaged moments temperature dependent: R114 (1,2-dichloro-1,1,2,2-tetrafluoroethane), with a moment ranging from 0.668 +/- 0.001 D at 308 K to 0.699 +/- 0.001 D at 410 K; and E134 (bis(difluoromethyl) ether), where the moment ranges from 1.739 +/- 0.002 D at 309 K to 1.840 +/- 0.001 D at 410 K. One refrigerant, R123a (1,2-dichloro-1,1,2-trifluoroethane), has a moment that in principle could be temperature-dependent but in fact is temperature-independent; its value is mu = 1.302 +/- 0.007 D. Accurate determination of a molecule's temperature-dependent dipole moment requires an independent determination of its electronic polarizability; this determination has been made from index of refraction measurements. Where possible, the present results are compared with earlier determinations of dipole moments.